By: Michael Camber
A Kentucky lumber mill was planning to add a new line, and the plant manager was looking into buying another air compressor. A colleague at a sister facility estimated they would need at least an additional 75 hp to meet the increased demands, so the plant manager requested pricing on 75 hp and 100 hp units. The existing system was based on a 40 hp modulating compressor, running nearly continuously.
After an initial site visit, a Kaeser territory manager suggested a compressed air audit, explaining that they should see what they were currently using before buying a much larger compressor. The plant might not be using all of the available capacity. They should first know the 40 hp unit’s load percentage and whether it was running even when they didn’t need it, wasting electricity and causing unnecessary wear and tear.
The customer agreed and the audit numbers came back—the specific power consumption was extremely high at 72.45 kW/100 cfm, and the existing system (prior to the expansion) could be run off a 20 hp compressor. The customer still couldn’t quite wrap his head around it—in his mind, the 40 hp one was running constantly to keep up with production demand. How could cutting the horsepower in half maintain steady pressure for the plant?
A 25 hp rental compressor was available, so the territory manager offered to prove it. The customer was still nervous, so the territory manager offered to keep the modulating compressor hooked up—just in case—and to sweeten the deal, promised a bottle of bourbon if it didn’t work out.
The first day of operation the customer called, convinced that the compressor wasn’t working properly because it kept turning off. The territory manager explained, “Exactly. Your other modulating compressor runs all the time, wasting your money. Ours shuts off when you don’t need it.”
After spending the day watching the compressor turn on and off without causing any low pressure problems in the plant, the customer really started to understand how much money he had been wasting. He replaced the 40 hp modulating unit with a 40 hp variable speed compressor which more efficiently covered the existing and the additional demand from the new milling line. No need to add 75 hp -100 hp.
A follow-up compressed air audit of the data in the compressor’s integrated Sigma Control 2™ controller confirmed the system’s performance. Previously, the lumber company was spending $13,400 in energy. Now, their costs are down to $4,052—even though their demand has increased. Part of the savings came from operating at a lower plant pressure; the average system pressure has been reduced from 113 psig to 105 psig.
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